IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 14, Issue 10 Ver. X (Oct. 2015), PP 85-90 www.iosrjournals.org

The Effectiveness of Transcutaneous Electric Nerve Stimulation (TENS) in The Management of Painful Diabetic Peripheral Neuropathy (DPN)-A critiquing Antony T., Merghani T.H. Faculty of Medicine, University of Tabuk, Kingdom of Saudi Arabia

Abstract: Background: The peripheral neuropathy is one of the common complications of type II diabetes mellitus along with other complications and affects both somatic and autonomic nervous system. The pharmacological treatment of diabetic peripheral neuropathy is mainly directed for symptom control with varying extent of the effectiveness. TENS is a less expensive, non-invasive procedure useful in neuropathic pain; however, the literature evidence for its effectiveness is inconclusive and contradictory. This article aimed for a critical analysis of the available evidence on the application of TENS for the clinical treatment of painful diabetic peripheral neuropathy patients. Methodology: An electronic search was carried out for the relevant literature published during the period of 2009 to 2014 in the databases. The selected evidence evaluated for quality and level of evidence using SIGN critiquing tool and Harbour and Miller 2001 hierarchy of evidence respectively. Results: Identified five relevant pieces of evidence for critical analysis. Three of them were systematic reviews, one randomized controlled trial and one observational study. Conclusion: The majority of the evidence recommends the use of TENS therapy for the management of painful diabetic peripheral neuropathy. However, it is limited with short duration of trial period and lack of standardization of TENS therapy for the condition. Keywords:TENS, Electrotherapy, Neuropathic pain, Diabetic neuropathic pain.

I.

Introduction

The peripheral neuropathy is one of the common complications of type II diabetes mellitus along with other complications affecting 60-70% of diabetic patients in varying extent from mild to severe forms (Charnogursky et al., 2014). As a heterogeneous disorder with complex pathophysiology, diabetic peripheral neuropathy (DPN) affects both somatic and autonomic nervous systems (Singh et al., 2014). The clinical symptoms are characterized with burning, tingling (pins and needles or paraesthesia) sensation, and shooting (like electric shock), or lancinating (stabbing) type of pain (Singh et al., 2014). The currently using pharmacological treatment of diabetic peripheral neuropathy is mainly directed for a symptom control rather than a curative therapy and the extent of the effectiveness varies in different patients (Brilet al., 2011; Charnogurskyet al., 2014). The National Institute for Health and Clinical Excellence (NICE) guidelines recommends the use of tricyclic antidepressants, selective serotonin and norepinephrine reuptake inhibitors, anticonvulsants, opioid agents and topical medications such as lidocaine patch and capsaicin for the pharmacological treatment of neuropathic pain. However, these agents are only able to partially control the symptoms, and they may cause serious adverse effects, which is a major role for the discontinuation of drug therapy in these patients (Charnogurskyet al., 2014). In addition to these complications of drug therapy, the limited availability of evidence, the low degree of cost-effectiveness and the little improvement in physical functioning limits the use of the pharmacological agents (Brilet al., 2011). On this context, it is logical to consider other effective treatment modalities such as TENS and electrotherapy for the management of painful diabetic peripheral neuropathy. TENS is a less expensive, widely used non-invasive procedure for the management of painful conditions, and it carries low incidence of complications(Tashani and Johnson, 2009). A modulation of gatecontrol of pain process (Melzack and wall, 1965) at the spinal level has been hypothesized as a mechanism for the analgesic effect of the TENS. It is also suggested that the modulating effect of TENS on the descending spinal inhibitory mechanism of pain and the application of TENS releases the endogenous opioids and affects the metabolism of other neurotransmitters such as GABA (Gamma Amino Butyric Acid), acetylcholine, serotonin, noradrenaline and adenosine (Tashani and Johnson, 2009), which may alter the pain experience at the spinal level. However, different kinds of literature provide an inconclusive and contradictory results on the effectiveness of TENS in the management of painful peripheral diabetic neuropathy. Therefore, it is relevant to

DOI: 10.9790/0853-1410108590

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The Effectiveness of Transcutaneous Electric Nerve Stimulation (TENS)inThe Management… carry out a critical appraisal of available evidence on the application of TENS for the clinical treatment of painful diabetic peripheral neuropathy patients.

II.

Literature Search Strategy

An electronic search was carried out for the relevant literature published during the period from 2009 to 2014 in the databases of COCHRANE Review, MEDLINE Ovid (from1996 to 2014 November 25), CINAHL PLUS, Scopus and EMBASE. The following search terms such as “Transcutaneous Electric Nerve Stimulation” “TENS” “pain” “Diabetic neuropathy” “diabetic peripheral neuropathy” were used along with appropriate boolean operators AND or OR. The search was limited for the articles, in English language and human adults. Also used forward as well as backward chaining for the relevant articles cited in retrieved publications. The primary screening identified 33 related articles and after an initial reading of title and abstract for relevant articles and avoiding duplication, retrieved eight articles for critical reviewing. Three articles were excluded from the analysis, as they were not acceptable according to SIGN checklist criteria for analysis of the internal validity of the evidence. Three of the selected literature are systematic reviews (2 of them with meta-analysis and one systematic review), one randomized controlled trial and one observational study. Figure (1) shows the flow chart of the literature search and Table (1) describes the features of the evidence that is selected for critical analysis. Analysis of Evidence in patients with diabetic peripheral neuropathy for the efficacy of TENS to reduce pain: In a systematic review with meta-analysis of randomized controlled trials, Stein et al.,(2013), evaluated and compared the effectiveness of the TENS and electromagnetic field use on the pain and measured the improvement of sensitivity in patients with painful diabetic peripheral neuropathy with placebo and other interventions. The authors carried out this systematic review in accordance with Cochrane collaboration and statement for systematic review and Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA), with the search for evidence in electronic databases such as Medline, LILACS, PEDro, EMBASE and Cochrane central register using predefined search terms and without language restriction. The features of the studies included for analysis are shown in Table:2. The total sample size from the studies was 173 with 96 patients in the TENS arm. The main outcome of the evaluation was pain relief with secondary outcomes of sensitivity and length of treatment. The investigators assessed the extent of bias involved in the analyzed studies and mentioned in the table, which increases the internal validity of the article. Of these reviewed articles, six of them used TENS as a treatment modality, which is the focus of this assignment. Five articles compared TENS with placebo and one study compared it with high-frequency muscle stimulation for its effectiveness. The included articles used different methodologies of TENS in treatment (see table 1), and this lack of uniformity further reduces the validity of the article. The meta-analysis of articles of placebo-controlled trials showed improvement in pain measurement (VAS) with a significant difference between intervention group and control group (p-value of 0.01, CI: 95% standard mean difference of -0.44 within the range of -0.79 to -0.09). The shortterm effectiveness was assessed with a sub-analysis of four studies with treatment period of 2,4, and 6 weeks, which showed improvement in pain (p-value =0.03 under CI: 95% standard mean difference of -0.54 within the range of -1.02 to -0.06), however, two studies with longer treatment period of 12 weeks were without significant reduction in pain with p value= 0.14 (with CI: 95% standard mean difference of -0.47 within the range of -1.10 to -0.16). This data questions the long-term efficacy of the TENS in pain relief with DPN. Overall, this study was conducted with a well-designed methodology with high degree rigor and internal validity. However, the main drawbacks involved with this evidence such as multi-focused assessment with different modalities of treatment, lack of uniformity in methods of treatment and a small number of patients in the included study trials affects negatively on the validity and reliability of the results. Finally, the publication bias involved with this meta-analysis could have been reduced with funnel plot test. Jin et al (2010) carried out a meta-analysis of RCTs with the aim to evaluate the effectiveness of transcutaneous nerve stimulation on diabetic peripheral neuropathy. Two investigators independently carried out the literature search in databases such as PubMed, EMBASE, Cochrane central register of controlled trials, CINAHL, and other relevant search engines. The literature search was based on pre-defined inclusion and exclusion criteria. The discrepancies between the investigators were resolved by consensus or third author adjudication. The use of Cochrane Handbook for Systematic Reviews of Interventions guidelines as a reference for this meta-analysis increased the validity and reliability of the article. The results of this article are expressed as relative risk ratio under 95% confidence interval and consideration of p value 0.5) after treatment. The pain disability index and CESD scale were similar in both groups after trial and during the follow-up period (p>0.5). The evidence concluded showed no significant difference between placebo group and treatment group. In an observational study,Moharic and Burger (2010) measured the extent of the improvement in small fibre function in diabetic peripheral neuropathy patients with TENS therapy. The authors enrolled the patients who fulfilled at least two items of Michigan Neuropathy Screening Instrument (MNSI) criteria, and used a standard method of Quantitative sensory testing (QST) to detect sensory abnormalities in the neurons. For comparison, the investigators obtained the normative data from age-comparable normal healthy volunteers using the same measurement procedures and instruments. In this evidence, the authors restricted the use of other therapeutic methods and drugs for neuropathic pain but allowed tricyclic antidepressants and selective serotonin reuptake inhibitors. The permission of these drugs during trial period might have affected the results, as these drugs have a neuro- stimulating effect. Thermal and pain thresholds were measured using Marstock method, vibratory perception threshold with Vibratory Sensory Analyzer 3000 and static touch threshold with von Frey’s hair. The total number of patients enrolled was 46, with 25 males and 21 females. The duration of diabetes and pain had great variation ranging from 2 to 36 years and 0.5 to 20 years respectively. This wide difference in basic data also might have influenced the result of this study. The intervention was carried out for 3 weeks with the application of TENS therapy for 3 consecutive hours daily. The patients were followed up for 1 month after treatment. The data analysis with SPSS15.0.1.1 for windows with a prefixed significant level of 5% showed two significantly changed measurements from baseline. The threshold for cold sensation is increased significantly DOI: 10.9790/0853-1410108590

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